Vapor-phase treatment of petroleum



June 18, 1940. T. B. LEI-:CH

'VAPOR-PHASE TREATMENT oF PETRQLEUM Filed June l0, 1938 Patented June 18,` 1940` UNiTED STATESN rArEN'r FFlCE I vAPoR-PHASE TREATMENT or PETROLEUM Application June 10, 1938, Serial No. 213,085

e Claims. (o1. 19e- 96) i My invention relates to the vapor-phase treatment of petroleum, more particularly to the removal of unsaturated bodies from `gasoline as polymers, and has for an object the withdrawal of the polymers from the system substantially i entirely free of gasoline.

In the production of gasoline (either straight run or cracked) suitable for motor fuel, it is` frequently desirable'to pass the gasoline in vapor phase through `treating towers charged with a suitable catalyst, such as fullers earth. The i catalyst produces" a selective polymerization of theunstable, unsaturated compounds which may then be separated from the gasoline vapor. Heretofore, the products of the polymerizing reaction, the polymers, were withdrawn from the system, as from `the bottom of each of a plurality of iractionating zones `or stages, such as bubble towers. The polymers so withdrawn contained a substantial amount of gasoline, which was either lost or recovered; recovered as by returningthe polymers to the vaporizer; or by passing them to an additional recovery system, in itself expensive as to rst cost and as to'loperation.

In accordance with my invention in one form thereof, the polymeraseparated from the gasoline vapors in the final fractionating zone, as in` ymersas a result of the reboiling which pass overhead from the intermediate bubble tower .i pass through a catalytic tower andto a further fractionating or separating zone. In this manner, the resultant product is entirely free of polymers and the polymers entirely free of gasoline.

The term gasolina as used herein and in the claims, is dened to mean those products, hydrocarbons, within the boiling range, and `having the characteristics, suitable for motor fuel-` For a morecomplete understanding of my invention, reference should now be had to the drawing, in which:

Fig. `l diagrammatically illustrates a system embodying my invention; and

Fig. 2 is a fragmentary view illustrating a `modication of the system of Fig. 1.

Referring to the drawing, gasoline in vapor mediate bubble tower I5.

. bubble tower I5.

phase, cracked or straight run, as produced from any of the several systems well known to those skilled in the art, passes through line III into the first treating stage or tower Il, charged with a suitable catalyst i2, such, for example, as iullers earth. The fullers earth, a clay catalyst which in size `is preferably equivalent to that which will pass through a 30 to 60 mesh screen, is supported on a perforated plate and screen I3. As the vapors pass downwardly through the cata1yst,` the unstable, unsaturated hydrocarbons arev polymerized. Ihe heavier polymers are removed from the bottom of the treating tower Il, and through line 54 are introduced into an inter- The vapors from the treating tower Il pass through line I6 into the bubble tower. Refined `gasoline is introduced into the bubble tower as reflux` through the line Il.

In the tower II some of the gasoline is entrained in the polymers. A part of such entrained gasoline may be separated therefrom in the bubble tower I5, and such` part that is not so separated, is recovered by provision of a reboiler I8 disposed in thel bottom of the intermediate The reboiler I0 may be heated in manner well understood by those skilled in the art,ias.f`or example, by passing through it a heating medium such as a heat-carrier gas, or hydrocarbon vapors or oil at a suitably high temperature toboil the polymers which temperature, by way of example and not by way of limitation, may range from 500 F. to 800 F. The heating medium enters through line I9 and is removed from the reboiler I through line 20. The polymers, entirely free of entrained gasoline, are removed from the intermediate bubble tower and from the system through line 2|.

` In lieu of the reboiler I8, built in or forming a part of bubble tower l5, a separate unit, reboiler Ia, Fig. may be provided, in whichcase the polymers and condensed and entrained gasoline from tower I5 pass by way of line I 8h into reboiler Iiid. The heating medium introduced by line I9 and removed through line 20 elevates the polymers to their boiling temperature, which maybebetween 500 F. and 800 F., more or less. In this manner, all gasoline present in the polymers is separated or stripped therefrom and by line [8c is returned to bubble tower I5. The gasoline-free polymers are removed `from the system by way of draw-olf line 2Ia.

The vapors introduced intokthe bubble tower I5 (and the gasoline separated from the polymers) pass upwardly therethrough, countercurnned gasoline, which gravitates downwardly from plate to plate. As well understood by those skilled in the art, there occurs in the bubble tower I a progressive separation between the f lower and higher boiling components. `The polymers are removed through line 2l, while the vaporous components are removed from the top of the bubble tower and through line 22 pass into a second treating stage or tower 23 containing a charge of fullers earth, or other catalyst line, are withdrawn through line 26 and are in-v troduced into the final fractionating zone or bubble tower 21. The vapors from tower 23 are withdrawnthrough line 28 and pass into bubble tower. 21. Reflux, as refined gasoline, is, through lines I1 and 2B, introduced into the bubble tower 21. Due to the selective separation within the bubble tower 21, refined gasoline, still in vapor phase, is removed from the bubble tower through overhead line 30. By suitable heat eX- change apparatus, as for example, a condenser 3|, the-gasoline is condensed and through line 32 introduced into an accumulator or storage tank 33. Alf-teined gasoline for storage is Withdrawn therefrom through line 34, controlled by valve 35. vRefluxis withdrawn from accumulator 33 under control of valve 36 and a reflux pump 31, both included in the line I1.

Though the `bubble towers l5 and 21 effectively separatethe polymers from` the lighter products, I have found that there may be entrained or condensed in the polymers collected in the bubble towers l5 and 21, gasoline in percentage as high as 3% lof the charge introduced into the system through line I0, though such proportion of gasorline may be even greater or less than 3%.

l In accordance with my invention the pnlymersA are withdrawn from the final separating or fractionating lZone of the system, as from the bubble tower 21, by line 33, elevated in pressure by pump 39, and returned to an intermediate zone of the system, as for example, b-ubble tower i5. By boiling ,to provide stripping in the intermediate zone, the polymers from the nal Zone of the system, all gasoline suitable for motor fuel, entrained, condensed, or otherwise present in the polymers, is separated or stripped therefrom.

The so separated gasoline then passes from thebubble tower l5 through its overhead line 22.

While I have shown two catalytic treating towers il and 23 and two fractionating stages l5 and 21, it is to be understood my invention is not limited thereto, as it comprehends the provision of any number of treating towers and bubble towers.

It is characteristic of my invention that the recovery of gasoline present in the polymers is accomplished without the addition of auxiliary heating apparatus, aside from the reboiler, and without the addition of other elements of a recovery system as heretofore proposed or uti- 2,204,685 rrent to and in contact with, the reux, the relized; and it is further characteristic of my invention that no additional load is placed upon the heating apparatus utilized toproduce the gasoline in vapor phase, which is introduced into charge line I0'.

By boiling the polymers in an-intermediate stage, bubble tower I5, any polymers which may pass out through overhead line 22 with the gasoline in vapor phase are condensed in tower 23 orl in the nal separating zone, tower 21, to insure the final product, refined gasoline, shall be free of polymers. v

While I have shown a particular embodiment of my invention, it will be understood that I do not limit myself thereto, since many modifications may be made, and I therefore contemplate by the appended claims to cover any such modications as follow within the spirit and scope of my invention.

What I claim is:

Ina vapor-phase process of polymerizing and removing ,undesirable constituents from gasoline by contacting vthe gasoline in vapor phase in a plurality of` stages under substantially the same lpressure with a polymer-producing catalyst, and in a separating Zone following each of said stages separating the polymers from the gasoline, the steps which comprise returning the polymers and ,the gasoline contained therein from thel bottom of the final separating zone to an intermediate separating zone, owing the polymers `and gasoline contained therein from LSU the bottom of the preceding treating stage to said intermediate zone, applying heat to the lower portion of v said intermediate separating Zone tionating tower for polymerizing in a plurality' of stages undesirable products from gasoline in vapor phase, of means including a conduit for return of 4polymers from the bottom of the final separating tower to an intermediate separating fractionating tower, means including a conduit for flow of polymers from bottom of said first catalytic tower to said intermediate separating tower, means f'cr applying heat to all of said polymers within the lower portion of said intermediate separating tower to boil them and thereby vaporize all gasoline present therein, means including a conduit connected to the bottom of said intermediate separating tower for withdrawing from said intermediate towerv gasoline-free polymers, and means for condensing and withdrawing from the last separating tower of the system polymer-free gasoline.

f THOMAS B. LEECH. 

